Electrochemical cells generally have a negative electrode, a positive electrode, and an electrolyte placed between the electrodes. The electrolyte is chosen so that transfer of ions between the two electrodes occurs, thus producing an electrical current. One example of an electrochemical cell is a rechargeable battery. The use of layered materials such as lithium cobalt oxide, LiCoO2, as the positive electrode in such a rechargeable battery is well established. The layered material consists of sheets of oxygen ions stacked one on top of the other. Between the first and second layers of oxygen are located the cobalt ions, with the lithium ions being located between the second and third oxygen layers. Use of LiCoO2 in rechargeable batteries allows greater energy storage per unit weight and volume than is possible in conventional rechargeable batteries such as nickel-cadmium. However LiCoO2 has disadvantages in that it is somewhat toxic, is less safe than is desirable, has limited energy storage capacity, and the cobalt containing materials from which it is produced are expensive and scarce.
Attempts have been made to use other compounds with a similar layered structure to that of, LiCoO2, such as LiNiO2, and LiFeO2. EP 0 017 400 discloses a range of compounds having layers of the α-NaCrO2 structure. In an International Patent Application, Publication No. WO97/26683, we disclosed the synthesis and viability of materials of the form QqMnyMzO2, where Q and M are each any element, y is any number greater than zero, and q and z are each any number greater than or equal to zero, and the material is a layered structure. It is one aim of the present invention to provide a further layered manganese oxide material which can be used in electrochemical cells.